Separation of naphthalene isomers



' June 3, 1952 PETROLEUM OIL S 1 J. E. NICKELS 2,598,715

SEPARATION OF NAPHTHALENE ISOMERS Filed Dec. 51, 19 48 DISTI LLATION l0 5cuT METHYL NAPHTHALENE xsonms V Z4 66H s0 ALKYLATION -I$OBUTYLENE f Z 5 22 DLSTILLATI O N 7 01* 1; -BuTYL-ALPHA -MEYHYL t- BUTTL-BETA METHYL NAPHTHALE NE: NAPHTHALENE CATALYST I AROMATIC sio m o rAccEPTon AROMATIC CATALYST DEALKYL ATION AccspTolf} ['3' 60 11 0 DE ALKYLATION v $3 LIQUID PHASE:

DISTILLATION v 50 DISTI LLATION LPHA METHYL 56 NA PHTHA LE NE- CRYSTALLIZEJZ y BETA METHYL NA PHTHA L EN E- INVENTOR.-

JOSEPH A. NICK Ls. fwwj I J's Patented June 3, 1952 UNITED STATES 50F]: [CE

scmrar cuqc nrneccmc .I QMEe Joseph=-E.-Nickels, Pittsburgh, =-Pa., assignor to lidppers Company, Inc., Pittsburgh, Pa., a. coroporation of'llelaware 1 This invention relates to the separation of alkyl naphthalene isomers particularlv alphaand beta-alkyl substituted isomeric naphthalenes in which the common substituenFalIQyI trated inthe accompanying drawing which is a flow sheet showing the various steps involved in separating and recovering alphaand betaisomers in purified form.

The alphaand beta-isomers of methylnaphthalene are found in coal tar distillates and in petroleum distillates." The cut containing the alph'aand beta-isomers c of rnethylna'phthalene may be separated by an efficient fractional disgroup is selected from the group consisting "of 5 till'ati on into a 5 out orfraction boiling between primary and secondary alkyl groups having from aboutl 240 and 245 C at atmospheric pressure. one to five carbon atoms. More part icularly generally the beta-isomer 'forms' the major porthe invention relates to the separation of alphation of the "mixture, that is yarying'irom 50% and beta-isomers of methylnaphthalene. Ihe to -75% ofthe mixture, most of'the remainder separation of the beta isomer' irom a mixture 10 being the alpha-isomer; of the alphaand beta methylnaphthalenes by -I have found that this mixture of alphaand freezing with erystallizationrhas been qui te 'satbeta-isomers of methylnaphthalene majf'bej s'epicfcctcryc cl zctiqn cc rc icn lih ,lcre cd' b' e k l fin h m 'wi h r a alpha-isomer from a mixtureof alphaandbetaolefine to form the corresponding tertiary-alkyl iccmcrc cf m t cchihclceci ac ncccccn'cc 15. cihr l cp ih cr c 'ic s cm c clk l ii isfactory. For example, theeutectic of a rnix- V a nixtureof alpha and beta-isomers orie'mol We of -pen bctc-nicthyleanh halcece. cf c buc l ncr a ficl r h fc 1 11 cf ,bc cbcut chcand i 1 %;bc. c:mci 1nan .mct ilcap ii e :i "form mcil crfic 'ythclcncbe Eb'ci rmc .ne hilaclc acd' c m' l f Bcccucc cf ma ,dificrcn c ic ccut 1 530. "icc cccylc crc ci with v e c7 'c lnlic h 'hy the boiling m rc u c c .clicalp e .cpdbctc- .n ccliihalclcc c 1 cm d l-vt'c cri bu M ch isomers, it i ,d t cu tt ciiccttncir. ciz rc .mc tiylcceb balc c c ci r c 't er ut by frac a cistil ct cn t .,gc -;12l1 .1i9mcr g ct m ihy ph h cc s c 'dxh rin' c primary Q i ct 9 r rcelwin m 112 v ..1 9. is to provide a,PrOW SiW-fifilfifillfi x5 1 3 'WP Jc'Q "i 1 the alphaa bc dsqmcrc.efwca sy na hthalenes.

her objec of th inYcnti nic-t p cvis a process v sc ar ciii ;ih c1nhr t iscmcrs c clkyl n nhiha twithsmie p or isomerizing the alphasomers. k A m Accordingly a h mcctr ,ihcuir vcnt iccceecc c hc iqi i c c icJmcliic i mpTc is to provide a proccs l rsfiwmt i h -en .m :Ecciiccicccct cr um. e c-'7 v beta-substituted naphthalene isomers. ylnaphthalene is nermaintjs'nquid, ,1 hereas'di- In the separation of alpha-h'and beta isomers tertiary butyI- aIpha ethylriaphthale e" is a of methylnaphthalene, th e isgrners arejalkylated sol id melti ngat 791C? V with isobutylene in the ,presence 'of a'n k xl U A fter thelalphaand beta-isomers have been catalyst such as 66 Be; sulphuricfacid separated by' distillation or 'crystall; ation they a mono-tertiary-butyl-beta-methylnaphtha he may be deallgylatedto formthe'alph v and a di-tertiary-FbutyIralpha-methylnaphtha- 40 meth ylnaphthaleneisomers"arid thuseffec't a lene are formed. These are new products which separation ofw theisomers; are good high-boiling solventaand iorm -inter- -;Ifhe process of separating the alphaand betamediate products ifor-the rnanuracture qf other isomers of methylnaphthalene accordance substituted naphthalenes. with thepreferijed proees may be carried out as With these and other objects in view the follows;inaking' 'rer rgneepo me;drawing invention consists in the process of: separating A closefraction'of coal tar oils orb u alphaand beta-isomers of alkyl nna'phthalenes oil containing the; hyl-naphthalefiejsomersis as hereinafter described and-more-partieularly introducedii lto'ad stillation tower" lfltb rhake defined in the claims. a close poiling cut of'- '240"-"to 245 5 Important featuresvof the invention are illuscut is colle'ctedinalreceiveifl iand then passed sulphonati'on orth'e'metffyliiaphthalnefbut sut- 1 f lization.

stantially no sulphonation takes place at tem-, peratures below 25 C. As explained above the.

alkylation of the methylnaphthalene isomer mixture with isobutylene reacts to form monotertiary-butyl-beta-methylnaphthalene and ditertiary-butyl-alpha-methylnaphthalene. A sufficient amount of isobutylene is used to supply one mol-ofisobutylene for each mol of betamethylnaphthalene and two mols of isobutylene for each mol of alpha-methylnaphthalene.

In place of the 66 B. sulphuric acid catalyst,v

other alkylation catalysts may be used such as phosphoric acid, boron trifluoride, hydrogen fluoride, aluminum chloride, aluminumbromide and.

ferric chloride. 1 a

In place of isobutylene any tertiary olefine having four to six carbon atoms to the molecule may be used for aklylating the alkylnaphthalene such as methyland ethylnaphthalenes. Fur ther the alkylation agent may be alcohols, alkyl .ihalidesror eth'ers which are capable of supplying j a tertiary, alkyl-g oup of four to six carbon atoms.

The mixture of alkylatedtertiary butylmethylf naphtha1ene isomers is then fractionally dis- 7 tilledin a still; {6 to take overhead through line l8, a! cut of tertiary-butyl-beta-methyl-naphi thalen e'to a receiver 20. A side out of di-tertiary-butyl-alpha-methylnaphthalene is withdrawnthrough line 22 to receiver 24. In some instances it may, however, be preferred to separate the tertiary alkylated isomers by crystal- The di tertiary:- butyl alpha methylnaphthalene is then dealkylated in a converter 26 to which is added a silica-alumina catalystand an aromaticcompound as an olefine acceptor. I

3 I havefound that a synthetic alumina-silica cata lyst containing from 50% to 99% silica and .50

to -1% alumina .is a satisfactory dealkylation catalyst, Other alumina-silica catalysts which arenatural clays, such as filtrol, and superfiltrol ,an acid-treated clay, are also satisfactory as 1 dealkylation catalystsL The silica-alumina contents o f th'ese clays comes withinthe scope of th synthetic alumina-silica catalysts above de. j

fined, The dealkylation step is carried out at a temperature of 150 to 250 C. under the vapor pressure of the mixture and is preferably carried out. at such a rate that the di-tertiarybutyl-alpha-methylnaphthalene isnot in contact with jthe catalyst for a longer period than fthreef'hoiirsf By this means the di-tertiary butylmethylnaphthalene may be deallrylated with a minimum amount of isomerization. The

isomerization reaction forms the beta-methylnaphthalene. The dealkylationmay also be performed in the vaporphase at 300 to 600 C.

1 either in the absence or presence ofinert atmospheres such as steam, n itrogen and carbon dioxide and/or olefine acceptors. .The acceptors which are most desirable in the present process .are; aromatic, compounds such as benzene,

tOIuene ethyIbenZene, phenol and cresol. These acceptors enterinto the reactionwhereby the butyl; molecule combines with the aromatic com-.-

pound when it is split off from the di-tertiarybutyl-alpha-methylnaphthalene.

a The alpha-methylnaphthalene formed in the dealkylation in converter 26 is then, passed to a still 28 for the purpose of separating the alphamethylnaphthalene from the reaction mixture,

this, product being collected in receiver 30.; In

order to avoid possibility of decomposition of the alpha methylnaphthalene the, -distillation is p era y 9a 'ri Ql1t 39 a s ishtv quum-i,; l

has been found, however, that with an efi'icient fractionating still a vacuum is not essential.

The tertiary butyl beta-methylnaphthalene collected in the receiver is passed to a dealkylation converter 32 where it is dealkylated at a temperature of 150 C. to 250 C. in the presence of an aluminum-silica catalyst, and an aromatic olefine acceptor or in the vapor phase at 300 to 600 C. as described above. The catalysts and acceptors for dealkylating the tertiary-butylbeta-methylnaphthalene are the same as the catalysts and acceptors used indealkylating the di-tertiary-butyl-alpha methylnaphthalene.

the dealkylated beta-methylnaphthalene content 7 of the receiver is comparatively high, that is 75% or more, a substantially pure beta-methylnaphthalene may be recovered by a distlllation" "in still 34; If thebeta-methylnaphthalene content from the-receiver 32 is or less, then the beta-methylnaphthalene recovered by an efficient distillation will vary from about to fbeta-methylnaphthalene. In order to obtain a practically pure beta, methylnaphthalene, the

distillation product is passed into a crystallizer 36 and cooled to a temperature of approximately --20 C. The beta-methylnaphthalene recovered from the crystallizer is passed to a receiver 38 and is practically pure product.

The di-tertiary-butyl-alpha-methylnaphthalene and the tertiary-butyl-beta-methylnaphthalene may be dealkylated in the liquid phase at h the temperature conditions described above.

However, if desired, the dealkylation may be carried out in the vapor phaseusing a synthetic alumina-silica catalyst either in the absence or presence of an inert atmosphere such as steam.

nitrogen and carbon dioxide. In the vapor phase ahigher temperature of 300 to 600 is required.

Other vapor phase dealkylation catalysts, such as naturally occurring clays andacid treated clays as described hereinbefore, may be used in place of the synthetic alumina-silica catalysts.

As an example of the butylation of an isomer 1 cut from coal tar containing an averageof 70% alpha-isomer and boiling between 240 and 245 0., 1510.2 grams of the isomer mixture was. alkylated in the presence of 457.6 grams of 66 B. sulphuric acid in an excess of isobutylene. From a the butylated mixture were obtained 18.7% by volume and 20.2% by weight of mono-tertiarybutyl-beta-methylnaphthalene boiling between 161 and 165 C. at 20 mm. pressure and 42.6%

by volume or 45.2% byfweight'of ditertiarybutyl-alpha-methylnaphthalene boiling between 193 and 200 'C. at 20 mm. pressure, The cut boiling between 193 and 200 was then dealkylated in the presence of superfiltrol as the catalyst under different times and pressures as shown in the following table'to' give the yields shown therein:

Asshown in the above table all tr has ha isome" of greater than 95 percent. 1 5 Q. l Pi purity One out boiling between 160 and 16590., obtained from the distillation or the butyl-ated meth lnaphthalene was deaikylated in the presence of superfiltrol with benzene as the acceptor. For example, 158 grams of the cut obtained by the distillation were dealkylated in the presence of 31.6 grams of supernltroi and 124'8 g-rams of benzene at a temperature or 260 C. for three hours to roduce a 93.9% yield (106.4 grains) of beta-methylnaph'thalene having a purity of 70.5%. When the product was carefully distilled through a highly 'efficieht column 60 grams of pure beta-methylnaphthalene were recovered.

By repeating this process using 158 grains of the cut boiling between 160 and 165 0., dealkylating in the presence of 1248 grams of benzene and 31.6 grams ofsiiper'filtrol at a temperature of 200 C. for three hours, 105 "grams'or 70.5% beta-methylnaphthalene was obtained. By cooling this mixture of beta-methylna htha lane to a temperature of -'=--20 and separating the crystals 63.5 grams of beta-'rnethyln'aphthalene of 95% purity were recovered.

In accordance with another examp1e'1l9 grams of the fraction boiling between 166' andl65 C. Was dealkylated in the presence of "1272 grams of ethylbenzene and 25 grams of superfiltrol for three hours at 175 C. By this action a "yield of 78.3% (66.9 grams) of beta methylnaphthalene containing 72.8% of beta 'isome'r -was-recovered. The ethylbenzene was used'as an efficient equilibrator in this example instead of benzene for production of beta-methylnaphthalene. By efficient distillation substantially 40.5 "grams of pure beta-methylnaphthalene 'wererecovered. I

In a second example using 119 gra ns o'fthe fraction boiling between 160 and 155 C. and dealkylating with 1272 grams of ethyibenzene i'nthe presence of 25 grams of superfiit'roi for three hours at 175 C., '77 grams of beta-methymaphthalene containing 72.8% beta-methylnaphthalene was recovered. By crystallization of this beta-methylnaphthalene when freezing at a temperature of 20 0., 46 grams of beta-methylnaphthalene were recovered having a purity of 96% beta-methylnaphthale'ne. I

In the above described process the alkylation products as well as the dealkylation products may be separated by distillation or by crystallization. In the claims these processes or'sepa'ration are defined as purification separation or physical separation. c H

In place of a mixture of isomers or metnyinaphthalene a mixture of 'alphaand betaisomers of ethylnaphthalene has been treated by 55 the same process using isobutylene as the alkylating olefine and sulphuric acid as the catalyst for alkylation. The alkylated ethylnaphthale'ne'isomers may then be dealkylated with a'superfiltrol catalyst at a temperature of 150 to 250 C. in the presence of an ethylbenzene acceptor. The yields obtained in the separation of the alphaand beta-ethylnaphthalene isomers are approximately the same as that obtained in the separation of alphaand beta-methylnaphthalene isomers.

The preferred form of the invention having been thus described, what is claimed as new is:

l. A method for the separation of the alpha isomer from a mixture of alphaand beta-alkyl substituted isomeric naphthalenes in which the common substituent alkyl group is selected from the group consisting of primary and secondary alkyl groups having from one to five carbon atoms which comprises forming a mono-tertiary alkyl derivative "of the beta-isomer and a ditertiary alkyl derivative of thealpha isomer by reacting said mixture with an alkylating agent containing a tertiary alkyl group having from four to six carbon atoms in the group, said alkylating agentbeing' present in an amount sufficient to furnish one mole of alkylating agent per mol'e'of beta-isomer reacted and two moles of alkylating agent per mole of alpha-isomer reacted, physically separating from the alkylated mixture the di tertiar alkyl derivative of the alpha isomer, and dealkylating the derivative so separated to produce the alpha isomer.

2. A method for the separation of the alpha isomer from a mixture of alpha-- and-b'e't'a isomers of methylnaphthalene which comprises I forming a mono tertia'ryalkyl derivative of the betaisomer and a di tertiary alkyl derivative or the alpha isomer by reacting said mixture with an alkyla'ting agent containing a tertiary alkyl group having from four to six carbon atoms in the group, said alkyl'at i'ng agent being present in an amount sufficient to furnish one mole of alkylat ing agent per'm'ole of beta-isomer rea'cted and two moles 'of alkylating agent per mole of alpha-' isomer reacted, physically separating from the alkylated mixture the di-tertiary'alkylderivative of the alpha isomer, and dealkylating the derivative so separated to produce the alpha isomer.

3. A method for the separation of the alpha isomer from a mixture of alphaand beta-isomers of ethylnaphthalene which comprises forming a mono-tertiary'alkyl derivative of the beta -isomer and a di-tertiary alkyl derivative of the alpha isomer by reacting said mixture with an alkylatin'g agent containing a tertiaryalkyl group having from four to six carbon atoms in the group, said alky'lating agent being present in an amount sufficient to furnish one. mole of alkylating agent per mole of beta iso'mer reacted and'two moles of 'alkylating agent per mole of alpha-isomer reacted, physically separating from the alkylated mixture the di tertiary alkyl derivative of the alpha isomer, and dealkylatingthe derivative so separated to produce the alpha isom r. 4. A method for the separation of the alpha isomer from a mixture of alphas and beta-alkyl substituted isomeric naphthalenes in which the common substituent alkyl group is selected from the group consisting of primary and secondary alkyl groups having from one to live carbon atoms which comprises forming a mono-tertiary alkyl derivative of the beta-isomer and a ditertiary alkyl derivative of the alpha isomer by reacting said mixture with an alkylating agent containing a tertiary alkyl grou'pha'ving from four to six carbon atoms in the group, said ,alkyl'ating agent being present in an amount sufficient to furnish one mole of alkylating agent per mole of beta-isomer reacted and two moles of alkylating agent per mole of alpha-isomer reacted, separating from the alkylated mixture the di-tertiary alkyl derivative of the alpha isomer, dealkylating the derivative so separated in the presence of an aromatic hydrocarbon as an olefin acceptor to produce the alpha. isomer, and producing purified alpha isomer by fractional distillation of the products of dealkylation.

5. A method for the separation of the alpha isomer from a mixture of alphaand beta-alkyl substituted isomeric naphthalenes in which the common substituent alkyl group is selected from the group consisting of primary and secondary alkyl groups having from one to five carbon atoms which comprises forming a mono-tertiary "derivative of the beta-isomer and a di-tertiary alkyl derivative of the alpha isomer by reacting said mixture with a tertiary alkene having from four to six carbon atoms'in the presence of sulfuric acid under alkylation conditions including a temperature in the range of to 25 C., said alkene being present in an amount suficient to furnish one mole of alkylating agent per mole of beta-isomer reacted and two moles of alkylating agent per mole of alpha-isomer reacted, physically separating from the alkylated mixture the di-tertiary alkyl derivative of the alpha isomer, and dealkylating the derivative so separated to produce the alpha isomer.

6. A method for the separation of alphaand beta-alkyl substituted isomeric naphthalenes in which the common substituent alkyl group is selected from the group consisting of primary and secondary alkyl groups having from one to five carbon atoms which comprises forming a mono-tertiary alkyl derivative of the beta-isomer and a di-tertiary alkyl derivative of the alpha isomer by reacting said mixture with an alkylating agent containing a tertiary alkyl group having from four to six carbon atoms in the group, said alkylating agent being present in an'amount sufficient to furnish one mole of alkylating agent per mole of beta-isomer reacted and two moles of alkylating agent per mole of alpha-isomer reacted, separating the di-tertiary alkyl derivative of the-alpha isomer and the mono-tertiary alkyl derivative of the beta-isomer by fractionally distilling the alkylated mixture, and separately dealkylating said derivatives so separated in the vapor phase in the presence of a silica alumina len and a di-tertiary-alkyl-alpha-methylnaphthalene by reacting said mixture with a tertiary 3 olefin having from four to six carbon atoms in the presence of sulfuric acid at a temperature in the range of 0 to 25C., said olefin being present in an amount sufficient to furnish one mole of olefin per mole of beta-methylnaphthalene reacted and two moles of olefinper mole of alpha-methylnaphthalene reacted, separating from the alkylated mixture a di-tertiary- -alkylalpha-methylnaphthalene fraction and a monotertiary-alkyl-beta-methylnaphthalene fraction by fractional distillation, and separately dealkylating said fractions to produce alphamethylnaphthalene and beta-methylnaphthalene.

BIA method for the preparation of alphamethylnaphthalene from a' mixture containing other hydrocarbons including beta-methylnaphthalene which comprises fractionally distilling tiary-butyl-beta-methylnaphthalene and di-tertiary-butyl-alpha-methylnaphthalene by treating said fraction with isobutylene in the presence of sulfuric acid under alkylation conditions and at a temperature in the range of 0 to 25 C., said isobutylene being present in an amount sufiicient to furnish one mole of isobutylene per mole of beta-methylnaphthalene reacted, and two moles of isobutylene per mole of alpha-methylnaphthalene reacted, fractionally distilling the alkylation products to produce a di-tertiary-butyl-.

alpha-methylnaphthalene cut, and dealkylating said out in the presence of a silica-alumina catalyst under liquid phase conditions at a temperature in the range of 150 to 250 C. to produce alpha-methylnaphthalene, and separating from the dealkylation products alpha-methylnaphthalene having greater than 'percent purity.

9. A method for the separation of alphamethylnaphthalene from a mixture thereof with beta-methylnaphthalene which comprises forming mono-tertiary-butyl-beta-methylnaphthalene and di-tertiary-butyl-alpha-methylnaphthalene by reacting said mixture with isobutylene under alkylation conditions, said isobutylene being present in an amount suificient to furnish one mole ofisobutylene per mole of beta-methylnaphthalene reacted, and two moles of isobutylene JOSEPH E. NICKELS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name. Date 1,767,302. Michel June 24, 1930 2,194,449 Sachanen et a1. Mar. 19, 1940 2,370,810 Morrell et al Mar. 6, 1945 2,436,110 Larsen Feb. 17, 1948 2,436,698 Oblad Feb. 24, 1948 OTHER REFERENCES Darzens et al., Compt. rend. 199, 1426-8 (1934),

Abstracted in Chemical Abstracts 29:18058. 

1. A METHOD FOR THE SEPARATION OF THE ALPHA ISOMER FROM A MIXTURE OF ALPHA- AND BETA-ALKYL SUBSTITUTED ISOMERIC NAPHTHALENES IN WHICH THE COMMON SUBSTITUENT ALKYL GROUP IS SELECTED FROM THE GROUP CONSISTING OF PRIMARY AND SECONDARY ALKYL GROUPS HAVING FROM ONE TO FIVE CARBON ATOMS WHICH COMPRISES FORMING A MONO-TERTIARY ALKYL DERIVATIVE OF THE BETA-ISOMER AND A DITERTIARY ALKYL DERIVATIVE OF THE ALPHA ISOMER BY REACTING SAID MIXTURE WITH AN ALKYLATING AGENT CONTAINING A TERTIARY ALKYL GROUP HAVING FROM FOUR TO SIX CARBON ATOMS IN THE GROUP, SAID ALKYLATING AGENT BEING PRESENT IN AN AMOUNT SUFFICIENT TO FURNISH ONE MOLE OF ALKYLATING AGENT PER MOLE OF BETA-ISOMER REACTED AND TWO MOLES OF ALKYLATING AGENT PER MOLE OF ALPHA-ISOMER REACTED, PHYSICALLY SEPARATING FROM THE ALKYLATED MIXTURE THE DI-TERTIARY ALKYL DERIVATIVE OF THE ALPHA ISOMER, AND DEALKYLATING THE DERIVATIVE SO SEPARATED TO PRODUCE THE ALPHA ISOMER. 